JP7401757B2 - Bending test method, jig and test specimen - Google Patents

Description

The present invention relates to a bending test method, a jig, and a test specimen.

A large moment is input to vehicle body parts such as the B-pillar during a collision. Therefore, parts to which such large moments are input are required to have excellent moment resistance.

The moment resistance performance of a component can be evaluated, for example, by a four-point bending test. Regarding the four-point bending test, various methods have been proposed to appropriately evaluate material properties.

For example, in the four-point bending impact test method disclosed in Patent Document 1, a test piece is placed on two support members arranged apart from each other, and the upper surface of the test piece is placed between the two support members. A rigid body is placed to cover the rigid body, and an impactor is caused to collide with the upper surface of the rigid body. Patent Document 1 describes that in the above configuration, by forming the rigid body to extend in the direction connecting the two support members, the test piece can be bent at four points regardless of the angle of impact of the impactor with the test piece surface. It is stated that it can be done.

Japanese Patent Application Publication No. 2017-116494

As disclosed in the above-mentioned Patent Document 1, the four-point bending test is generally performed by applying a load to the upper surface of the test specimen. However, when a load is applied to the upper surface of the specimen, the cross-sectional shape of the specimen may change significantly at the portion where the load is applied. As a result of research conducted by the present inventors, it has been found that when the cross-sectional shape of the test specimen changes significantly in this way, moment resistance performance may not be appropriately evaluated.

Therefore, an object of the present invention is to provide a bending test method, a jig, and a test specimen that can suppress changes in the cross-sectional shape of the test specimen.

The gist of the present invention is the following bending test method, jig, and test specimen.

(1) A method of conducting a bending test on a test specimen having a top plate portion and a pair of side wall portions extending downward from both ends of the top plate portion in the width direction, the method comprising:
an installation step of installing a test specimen to which a jig is attached on a pair of support members spaced apart from each other in the horizontal direction;
a loading step of applying a bending load to the test specimen installed on the pair of support members,
The jig has a pair of load transmission parts having an inverted U shape,
The pair of load transmission parts are arranged in a longitudinal direction of the specimen and cover the specimen from the top plate side, and are fixed to the pair of side walls of the specimen. ,
In the bending test method, in the loading step, a bending load is applied to the test specimen by applying a downward load to the load transmission portion.

(2) The bending test method according to (1) above, wherein a gap is formed between the top plate part and each of the load transmission parts in the vertical direction.

(3) In the loading step, a load is applied to each of the pair of load transmission parts by a pair of indenters,
According to (1) or (2) above, the distance between the tips of the pair of indenters in the longitudinal direction of the test specimen is set to be larger than the width of the top plate portion and the height of the pair of side wall portions. bending test method.

(4) The bending test method according to any one of (1) to (3) above, wherein each of the pair of load transmitting parts is fixed to the pair of side wall parts by weld metal, an adhesive, or a fastening member.

(5) The jig used in the bending test method described in any one of (1) to (4) above.

(6) The test specimen to which the jig described in (5) above is attached.

According to the present invention, it is possible to suppress changes in the cross-sectional shape of a test specimen when performing a bending test.

FIG. 1 is a diagram for explaining the bending test method according to this embodiment. FIG. 2 is a diagram for explaining the bending test method according to this embodiment. FIG. 3 is a perspective view showing the test specimen and the jig. FIG. 4 is a diagram for explaining the attachment process. FIG. 5 is a diagram for explaining the loading process. FIG. 6 is a diagram showing another example of the test specimen. FIG. 7 is a diagram showing another example of the test specimen. FIG. 8 is a diagram showing another example of the load transmission section. FIG. 9 is a diagram showing another example of the load transmission section.

A bending test method according to an embodiment of the present invention will be described below. FIGS. 1 and 2 are diagrams for explaining the bending test method according to the present embodiment. Specifically, FIG. 1 is a perspective view showing a test specimen 10, a jig 20, and a test device 30, which will be described later, and FIG. 2(a) is a front view showing a test specimen 10, a jig 20, and a test device 30. 2(b) is an enlarged sectional view showing the BB section in FIG. 2(a), and FIG. 2(c) is an enlarged sectional view showing the CC section in FIG. 2(a). It is a diagram. In addition, in FIG. 2(b) and FIG. 2(c), illustration of some structures of the jig 20 and the testing apparatus 30 is omitted in order to avoid complicating the drawings.

As shown in FIGS. 1 and 2, in the bending test method according to the present embodiment (hereinafter simply referred to as the test method), a test specimen 10 is subjected to a bending test using a jig 20 and a testing device 30. will be held. As the testing device 30, various known testing devices used for bending tests can be used. Therefore, although detailed description is omitted, in this embodiment, the testing apparatus 30 includes a pair of indenters 32a, 32b and a pair of support members 34a, 34b. Hereinafter, after explaining the test specimen 10 and the jig 20, the test method according to the present embodiment will be explained.

(Configuration of test specimen)
FIG. 3 is a perspective view showing the test specimen 10 and the jig 20. As shown in FIGS. 1 to 3, in this embodiment, the test specimen 10 has a rectangular tube shape, and extends downward from the top plate portion 12 and both ends of the top plate portion 12 in the width direction Y. It has a pair of side wall portions 14a, 14b, and a bottom plate portion 16 that connects the lower ends of the side wall portions 14a, 14b.

In addition, in this specification, the top plate part, the side wall part, and the bottom plate part are named based on the positional relationship when the bending test is performed. Therefore, for example, when the test object is a part such as a car body, the top plate part of the test object does not need to be the top plate part even when used as a part. In other words, the top plate portion of the test specimen may be a portion that becomes a side wall portion or a bottom plate portion when used as a component.

(Jig configuration)
The jig 20 has a pair of load transmitting parts 22a, 22b and a pair of load supporting parts 24a, 24b. The load transmitting parts 22a, 22b and the load supporting parts 24a, 24b are made of, for example, a metal material (such as steel). Each of the load transmitting parts 22a and 22b has an inverted U shape. In this embodiment, the load transmitting parts 22a and 22b have the same configuration, and each includes a top plate part 40 and a pair of plate-shaped fixing parts 42a and 42b extending downward from the top plate part 40. .

Each of the load supporting parts 24a and 24b has a U-shape. In this embodiment, the load supporting parts 24a and 24b have the same configuration, and each includes a bottom plate part 44 and a pair of plate-shaped fixing parts 46a and 46b extending upward from the bottom plate part 44.

Note that the materials, dimensions, etc. of the load transmitting parts 22a, 22b may be determined as appropriate so that the load can be appropriately transmitted from the indenters 32a, 32b to the test specimen 10 in the loading process described later. Further, the material, dimensions, etc. of the load supporting parts 24a, 24b may be determined as appropriate so that the test specimen 10 can be appropriately supported in the loading process described later.

(Test method)
The test method according to this embodiment includes an attachment process, an installation process, and a loading process. FIG. 4 is a diagram for explaining the attachment process, and FIG. 5 is a diagram for explaining the loading process.

(Installation process)
As shown in FIGS. 3 and 4, in the attachment process, the load transmitting parts 22a and 22b are arranged so as to cover the test specimen 10 from the top plate part 12 side. Further, load supporting parts 24a and 24b are arranged so as to cover the test specimen 10 from the bottom plate part 16 side. The load transmitting parts 22a and 22b are arranged so as to be lined up in the longitudinal direction X inside the load supporting parts 24a and 24b in the longitudinal direction X of the test specimen 10. In the present embodiment, in the longitudinal direction X, the load transmission section 22a is provided on one side of the center of the test object 10, and the load transfer section 22b is provided on the other side of the center of the test object 10. The load support part 24a is provided at one end of the test body 10 in the longitudinal direction X, and the load support part 24b is provided at the other end of the test body 10 in the longitudinal direction X.

As shown in FIGS. 2(a) and 2(b), in this embodiment, the fixed portions 42a of the load transmitting portions 22a, 22b are fixed to the side wall portion 14a of the test specimen 10, and the fixed portions of the load transmitting portions 22a, 22b are 42b is fixed to the side wall portion 14b. Furthermore, as shown in FIGS. 2(a) and 2(c), the fixed parts 46a of the load supporting parts 24a and 24b are fixed to the side wall part 14a, and the fixed parts 46b of the load supporting parts 24a and 24b are fixed to the side wall part 14b. be done. In this embodiment, the fixing parts 42a, 42b, 46a, 46b are welded to the side wall parts 14a, 14b. Note that the welding method is not particularly limited, and various known welding methods (for example, arc welding) can be used.

As shown in FIG. 2(a), in this embodiment, one edge and the other edge of the fixing parts 42a and 46a in the longitudinal direction is joined to. Similarly, referring to FIGS. 2(b) and 2(c), one edge and the other edge of fixing portions 42b and 46b in longitudinal direction X are respectively joined to side wall portion 14b by welding portion 50. has been done. Note that, in order to avoid complicating the drawings, the welded portion 50 is not shown in any drawings other than FIG. 2.

As shown in FIG. 2(a), in this embodiment, the lower edge 43 of the fixing portion 42a is preferably not welded to the side wall portion 14a. Similarly, it is preferable that the lower edge of the fixed part 42b is not welded to the side wall part 14b. In this case, when a bending load is applied to the test specimen 10 in the loading process described later, it is possible to suppress the application of compressive force to the regions below the fixing parts 42a, 42b in the side wall parts 14a, 14b. Thereby, the test specimen 10 can be smoothly bent and deformed.

In this embodiment, the welded portion 50 is formed on the side wall portions 14a and 14b so as not to reach the top plate portion 12 and the bottom plate portion 16. The length (length in the vertical direction) and width (length in the longitudinal direction etc.) is preferably set appropriately.

As shown in FIG. 2(b), in this embodiment, a gap is formed between the top plate part 12 and the load transmission part 22a (more specifically, the top plate part 40) in the vertical direction. There is. As shown in FIG. 1, a gap is similarly formed between the top plate part 12 and the load transmission part 22b (more specifically, the top plate part 40). Further, as shown in FIG. 2C, a gap is formed between the bottom plate part 16 and the load support part 24a (more specifically, the bottom plate part 44) in the vertical direction. As shown in FIG. 1, a gap is similarly formed between the bottom plate part 16 and the load support part 24b (more specifically, the bottom plate part 44). These gaps are preferably 1 mm or more, more preferably 2 mm or more.

(Installation process)
As shown in FIG. 1, in the installation process, the test specimen 10 with the jig 20 attached is placed on support members 34a and 34b that are spaced apart from each other in the horizontal direction (longitudinal direction X of the specimen 10). Install. In this embodiment, the load supporting parts 24a, 24b are placed on the supporting members 34a, 34b.

(load process)
In the loading step, a bending load is applied to the test specimen 10 placed on the support members 34a and 34b. In this embodiment, as shown in FIG. 5, a bending load is applied to the test specimen 10 by applying a downward load from the indenters 32a, 32b to the top plate parts 40 of the load transmitting parts 22a, 22b. be done. In this embodiment, in the loading step, a static load may be applied from the indenters 32a, 32b to the load transmitting parts 22a, 22b, or an impact load may be applied.

Note that with reference to FIG. 2(a), when the distance D between the tips of the indenters 32a and 32b in the longitudinal direction The load required to bend and deform the test specimen 10 increases. Therefore, it is preferable that the distance D is set larger than the width of the top plate section 12 and the height of the side wall sections 14a and 14b.

(Effects of this embodiment)
In this embodiment, when performing a loading process on the test piece 10, a bending load is applied to the test piece 10 from the indenters 32a, 32b via the load transmitting parts 22a, 22b. Here, the load transmitting parts 22a and 22b are fixed to the test specimen 10 not at the top plate part 12 but at the side wall parts 14a and 14b. Therefore, in this embodiment, it is possible to bend and deform the test specimen 10 by applying a load from the indenters 32a, 32b to the side walls 14a, 14b via the load transmitting parts 22a, 22b (fixed parts 42a, 42b). can.

In this case, compared to the conventional four-point bending test in which the test specimen is bent and deformed by applying a load from the indenter to the top plate portion of the test specimen, the portions to which the load is applied (in this embodiment, the load transmitting portion 22a, 22b and the side wall portions 14a, 14b), deformation of the cross-sectional shape of the test specimen 10 can be suppressed. Thereby, an appropriate bending moment can be applied to the test specimen 10 between the load transmitting portion 22a and the load transmitting portion 22b. As a result, the moment resistance performance of the test specimen 10 can be appropriately evaluated.

In particular, in this embodiment, a gap is formed between the top plate part 12 and the load transmitting parts 22a, 22b (top plate part 40) in the vertical direction. Thereby, when carrying out a loading process with respect to the test object 10, it can suppress that the load transmission parts 22a and 22b contact the top plate part 12. As a result, deformation of the cross-sectional shape of the test specimen 10 can be sufficiently suppressed.

Note that the top plate portion 12 and the load transmitting portions 22a, 22b (top plate portion 40) may be in contact with each other. Even in this case, the load applied from the indenters 32a, 32b to the load transmitting parts 22a, 22b can be mainly transmitted to the side walls 14a, 14b. In other words, the load applied from the load transmission parts 22a, 22b to the side wall parts 14a, 14b can be made sufficiently larger than the load applied to the top plate part 12 from the load transmission parts 22a, 22b. Thereby, changes in the cross-sectional shape of the test specimen 10 can be suppressed.

Further, in this embodiment, the welded portion 50 is formed on the side wall portions 14a and 14b so as not to reach the top plate portion 12 and the bottom plate portion 16. In this case, when carrying out the loading process on the test specimen 10, it is assumed that the load is directly applied from the load transmission parts 22a and 22b to the vicinity of the top plate part 12 and the vicinity of the bottom plate part 16 via the welded part 50. It can be prevented. This can suppress deformation of the vicinity of the top plate part 12 and the vicinity of the bottom plate part 16 when carrying out the loading step. As a result, an appropriate load can be applied to the test specimen 10 in the vicinity of the top plate portion 12 and the bottom plate portion 16, and the moment resistance performance of the test specimen 10 can be evaluated more appropriately.

Moreover, in this embodiment, when carrying out a loading process to the test object 10, the test object 10 is supported by the support members 34a and 34b via the load support parts 24a and 24b. Here, the load supporting parts 24a and 24b are fixed to the test specimen 10 not at the bottom plate part 16 but at the side wall parts 14a and 14b. Thereby, deformation of the bottom plate portion 16 when a bending load is applied to the test specimen 10 can be sufficiently suppressed. Note that the load support portions 24a and 24b may not be provided. That is, the test specimen 10 may be placed directly on the support members 34a, 34b. Even in this case, deformation of the cross-sectional shape of the test specimen 10 in the vicinity of the joints between the load transmitting parts 22a, 22b and the side walls 14a, 14b can be sufficiently suppressed. Therefore, the moment resistance performance of the test specimen 10 can be appropriately evaluated.

(Other embodiments)
In the above-described embodiment, the load transmitting parts 22a, 22b and the load supporting parts 24a, 24b are fixed to the side walls 14a, 14b by welding, but the load transmitting parts 22a, 22b and the load supporting parts 24a, 24b are The method of fixing to the test specimen 10 is not limited to welding. For example, the load transmitting parts 22a, 22b and the load supporting parts 24a, 24b may be fixed to the side walls 14a, 14b using an adhesive. In this case, the application area and type of adhesive may be appropriately determined so that the load transmitting parts 22a, 22b and the load supporting parts 24a, 24b do not peel off from the side walls 14a, 14b during the loading process. Further, for example, the load transmitting parts 22a, 22b and the load supporting parts 24a, 24b may be fixed to the side walls 14a, 14b using fastening members such as bolts and nuts.

In the above-described embodiment, a case has been described in which the test specimen 10 has a rectangular tube shape. However, the test method according to the present invention includes a top plate portion and a pair extending downward from both ends in the width direction of the top plate portion. It can be used when performing a bending test on a specimen having a side wall portion of Therefore, the test method according to the present invention can also be used for a test specimen 10a having an inverted U-shaped cross section, for example, as shown in FIG.

For example, as shown in FIG. 7, a test specimen 10b having a hat-shaped cross section and having a pair of flange portions 18a and 18b extending in the width direction Y of the top plate portion 12 from the lower end portions of the side wall portions 14a and 14b may be used. , the test method according to the present invention can be used. Note that when performing a bending test on a test specimen 10b having a hat-shaped cross section as shown in FIG. The flange portions 18a and 18b may be supported by the flange portions 18a and 18b.

In the embodiment described above, a case has been described in which the side wall portions 14a, 14b are formed to extend parallel to the vertical direction, but the side wall portions 14a, 14b may be inclined with respect to the vertical direction. In this case, the fixing parts 42a, 42b, 46a, 46b may be inclined with respect to the vertical direction along the side walls 14a, 14b.

In the above-described embodiment, the case where the width of the top plate part 40 (the length in the longitudinal direction X of the specimen 10) and the width of the fixing parts 42a, 42b (the length in the longitudinal direction X of the specimen 10) is equal is explained. However, as shown in FIG. 8, the width of the fixing portion 42a and the fixing portion 42b (not shown in FIG. 8) may be smaller than the width of the top plate portion 40. In this case, by increasing the width of the top plate portion 40, sufficient strength of the top plate portion 40 against the load applied from the indenters 32a and 32b can be ensured. Moreover, by reducing the width of the fixing parts 42a, 42b, the fixing parts 42a, 42b and the side walls 14a, 14b can be joined in a smaller area in the longitudinal direction X of the test specimen 10. Thereby, the test specimen 10 can be bent and deformed more smoothly.

In the above-described embodiment, a case has been described in which the load transmitting parts 22a and 22b are separate members, but as shown in FIG. 9, the top plate part 40 of the load transmitting part 22a and the top plate part of the load transmitting part 22b 40 may be integrally formed. In this case, the integrally formed top plate portion 40 can be pressed by one indenter.

According to the present invention, it is possible to suppress changes in the cross-sectional shape of a test specimen when performing a bending test.

10, 10a, 10b Test specimen 12 Top plate part 14a, 14b Side wall part 16 Bottom plate part 20 Jig 22a, 22b Load transmission part 24a, 24b Load support part 40 Top plate part 42a, 42b Fixing part 44 Bottom plate part 46a, 46b Fixing Part 50 Welded part

Claims (6)

A method of performing a bending test on a test specimen having a top plate portion and a pair of side wall portions extending downward from both ends in the width direction of the top plate portion, the method comprising:
an installation step of installing a test specimen to which a jig is attached on a pair of support members spaced apart from each other in the horizontal direction;
a loading step of applying a bending load to the test specimen installed on the pair of support members,
The jig has a pair of load transmission parts having an inverted U shape,
The pair of load transmission parts are arranged in a longitudinal direction of the specimen and cover the specimen from the top plate side, and are fixed to the pair of side walls of the specimen. ,
In the loading step, a bending load is applied to the test specimen by applying a downward load to the load transmitting portion and applying the load to the pair of side wall portions . The bending test method according to claim 1, wherein a gap is formed between the top plate portion and each of the load transmission portions in the vertical direction. In the loading step, a load is applied to each of the pair of load transmission parts by a pair of indenters,
The bending test according to claim 1 or 2, wherein the distance between the tips of the pair of indenters in the longitudinal direction of the test specimen is set to be larger than the width of the top plate portion and the height of the pair of side wall portions. Method. 4. The bending test method according to claim 1, wherein each of the pair of load transmission parts is fixed to the pair of side wall parts by weld metal, an adhesive, or a fastening member. The jig used in the bending test method according to any one of claims 1 to 4. The test specimen to which the jig according to claim 5 is attached.

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